Doffer comb mechanism



1956 w. w. WRIGHT EI'AL 2,772,446

DOFFER COMB MECHANISM Filed Jan. 6. 1954 INVENTORS ATTORNEY United States Patent O DOFFER COMB MECHANISM Walter W. Wright and Glen P. Robinson, In, Atlanta, Ga.

Application January 6, 1954, Serial No. 402,543

2 Claims. (Cl. 19-406) This invention relates to doifer comb mechanism for carding machines, and it has particular reference to an improved arrangement for mounting and oscillating, reciprocating or vibrating the doffer comb.

In the past it has been the general practice to arrange the comb, constituted as a thin, toothed blade, for operative oscillating, reciprocating or vibrating motion in relation to the card clothing of the carding machine, upon the free ends of arms or levers extending radially from a rock shaft mounted for oscillation in bearings fixed to the machine frame and having at least one of its ends provided with oscillation-imparting means, commonly called the comb box, which include mechanically driven cam and yoke means running in a bath of lubricant.

Obviously, such a mechanism, which normally functions to oscillate or vibrate the dolfer comb through an arc of about 20 degrees at a frequency of between twenty and thirty cycles per second, is subject to considerable wear and, in normal operation, must be oiled at least once a day and overhauled at least once a year. Moreover, leakage of oil at the comb box, which it is practically impossible wholly to prevent, sometimes results in fouling, discoloring, or other injury of the material operated upon by the machine, with accompanying annoyance and possible loss.

In order to eliminate the oscillatory rock shaft and its attendant disadvantages there is disclosed and claimed in the patent of the present applicant, Glen P. Robinson, Jr., for Dolfer Comb Mechanism, No. 2,594,497, issued April 29, 1952, an arrangement wherein the comb member is mounted upon the free, oscillatable ends of a plurality of flexible, inherently resilient, or springy, arms, the opposite ends of the arms being secured rigidly to a support preferably aflixed to the frame of the machine. For oscillating the arms, and hence also the comb memher, an electromagnetic device is associated with each arm intermediate its ends to cause the arm to be inter mittently attracted to it as it is intermittently energized, the construction according to the above-identified patent has been found to have some operational disadvantages mainly attributable to the particular arrangement of the electromagnetic motor and its driving relation to the arm carrying the comb member. In the arrangement according to the patent, the electromagnetic units include U- shaped cores rigidly attached to the supporting bar for the springy arms and mounted so asto exert an attractive force on armatures affixed to the upper surfaces of these arms. These electromagnetic units were preferably energized by pulses of current occurring at a rate of thirty cycles per second so as to sustain the thirty cycle me chanical flexing oscillation of the arms and with them vertical oscillation of the comb. Since most power 'systerns operate on a frequency of sixty cycles per second, it was accordingly necessary to introduce an electronic frequency dividing apparatus between the current source and the electromagnetic devices.

Another disadvantage is that at mechanical resonance at which this system operates, the amplitude of the mechani- 2,772,446 Patented Dec. 4, i956 cal oscillation could be excessive, so that the armatures of the springy arms carrying the comb member might strike the pole pieces of the electromagnetic device. There was thus no way of controlling the stroke of the comb member without either allowing such striking contact or carefully controlling the natural mechanical resonant frequency of the system.

The improved construction according to the present invention eliminates the necessity for providing a fre quency divider unit in that the comb member will vibrate at half the frequency of the applied electrical power. Thus, if the frequency of the power source is the standard sixty cycles, the comb member will vibrate at the desired frequency of thirty cycles; Moreover, the springy arms are related to the pole pieces of their electromagnetic motors in such manner that there is nothing for the armatures and the arms to strike as they oscillate. The stroke of the arms is also stabilized so that should the armatures secured to them overshoot the pole pieces, they will be pulled back by magnetic forces. Also, the mechanical frequency of the arms, with the armatures and comb assembly carried by them, is preferably made higher than thirty cycles, or one half the electrical frequency of the power supply. Consequently the system will not be a resonant one and hence will be less sensitive to small changes in loading and springy arm constants.

In addition to the improvement in the construction of the electromagnetic motor, the present invention features also a change in the shape of the springy arms. In the mechanism of the above-mentioned patent the arms are of uniform width throughout their length. In the present improvement the arms are uniformly tapered, being widest at their fixed rear ends and narrowest at their free ends to which the latter the comb member is attached. The principal advantage of the new springy arm design is that the stress experienced by the arms in bending is distributed uniformly throughout their length, whereas with the arms of uniform width the stress was concentrated at the fixed ends of the arms. Reduction of the maximum stress which is effected by the new tapered arm design renders the same more resistant to fatigue during continuous operation over long periods of time.

Another advantage attendant in the new arm design is that the amount of weight which must be kept in oscillation is decreased to the extent of the material eliminated in the tapering.

More particularly, the improved electromagnetic driving device for the comb member features a laminated soft iron armature attached to each springy arm near its free narrow end. This armature is acted upon by an electromagnetic field set up across the armature between two pairs of poles located respectievly above and below the rest or neutral position of the arm. For producing the magnetic field across the pole pieces the electro magnetic device includes a winding on the core connected through a half-wave rectifier to an alternating current power source preferably of sixty cycles. The half-wave rectifier action causes the winding to be energized with sixty pulses per second. The first pulse acts to pull the armature and the spring arm to which it is attached from is rest position in which it is unstressed toward one pair of pole pieces tending to align the armature horizontally between the pole pieces. When the first pulse is terminated, the inherent springy restoring force in the arm causes the latter to be pulled back in the opposite direc tion to and pass its neutral position, and the next pulse causes the armature and arm to be attracted to the other pair of pole pieces. The mechanical resonant frequency of the arms, armatures and comb assembly is made higher than thirty cycles per second or one-half of the electrical driving frequency in order that the arm-atures and arms armors will be certain to return to or pass the neutral position and thus the armatures will be in the fields of the other pairs of the pole pieces when the next pulse is applied. The armatures and hence the arms, and the comb memoer carried thereby, will thus execute one complete oscillation for each two driving pulses. Since the latter occur at a rate of sixty times per second, the springy arms and their attached armatures, and hence the comb member, will oscillate at a rate of thirty cycles per second, which is the conventional frequency of operation.

In the accompanying drawing illustrating the invention, in the several figures of which like parts are similarly designated,

Fig. 1 is a top plan view illustrating one of the chosen plurality of tapered spring arms, the comb member at tached thereto at the narrow end of the arm, the fixed support means to which the opposite end of the arm is secured, and the electromagnetic motor located adjacent to the narrow end of the arm and which serves to oscillate the latter and hence also the comb member in predetermined relation to the card clothing of a carding machine,

Fig. 2 is a side elevation of the organization shown in Fig. 1,

Fig. 3 is an end elevation of the Fig. 1 organization as seen from the comb end, with a portion of the comb broken away, and

Fig. 4 is a fragmentary transverse sectional elevation taken through the electromagnetic motor on line 4-4 of Fig. 2.

The mechanism of the invention comprises essentially a doffer comb member 1 of somewhat conventional form preferably rigidly affixed by rivets 2, or the like, to the narrow, free ends 3 of a chosen plurality of flexible, inherently resilient or springy, thin, fiat, tapered, uniformly bending arms 4, the opposite, wide ends 5 of which are preferably secured to rigidly fixed support rail means 6 by bolts 6a. The rail means 6 are preferably carried by the frame (not shown) of the carding machine. Although only one of the arms 4 has been illustrated it will be understood that as has hereinbefore been indir cated, and as is shown in the prior patent referred to, a plurality of such arms are arranged along the length of the comb member and secured thereto in like manner.

It has been found satisfactory to make the arms 4 from 1095 l6-gauge carbon steel, and they are preferably about 4 /2 inches wide at their broad ends which are secured to the rail means 6 and /2 inch wide at the narrow end to which the comb member 1 is secured, and of a length appropriate to the installation requirements but proper to produce what is technically known as a uniformly bending spring.

In order to impart to the arms 4 controlled vibratory oscillation which will result in the desired oscillation or reciprocation of the comb means or member 1 relatively to the card clothing (not shown), there is provided in operative relation to each arm electromagnetic means in the form of a motor 7. Each of the motors 7 includes a laminated core 8 secured by bolts or the like 9 to bars 10 which may in turn be secured to the frame of the carding machine, and insulating pads 11 are interposed between the cores 8 and bars 10.

As is clearly shown in Fig. 3, each bore 8 includes two pairs of pole pieces 8a, 8b and 8c, 8d in confronting spaced relation at the sides of the respective arm 4 adjacent to the end thereof to which the comb member 1 is secured, the pole pair 8a, 81) being located above the pole pair 8c, M. A laminated armature 12 of soft iron secured above and below such arm 4 near the narrow, comb member carrying end thereof is arranged for motion with, and to impart motion to, the arm in a. direction perpendicular to the plane of the arm in the free space between the two pairs of pole pieces. A coil 13 surrounds one leg of the motor core 8 for producing the magnetic flux therein and is energized intermittently, such as for example from a conventional 60 cycle, alternating current power supply indicated by terminals 14,

through a half wave rectifier device 15 which can be of the dry disc type such as the well known copper oxide unit.

In an unenergizcd condition of the coil 13, the armature 12 occupies a neutral position between the two pairs of pole pieces 8a, 8b and 8c, 8d, and the spring arm 4 is unstressed.

When the coil 13 is energized, the first pulse of rectified current put through the same during the positive half of the first cycle of the applied alternating current will cause the armature 12 and arm 4 to be pulled from its neutral position toward one pair of pole pieces 8a, 8b, tending to align the armature horizontally between those pole pieces. During the negative half of that first cycle, the rectifier 15 does not conduct, there is thus no electromagnetic pull on armature 12, and the latter is thus pulled back by the restoring force built up in the spring arm 4 toward its neutral position, slightly passing the latter in the direction of the other pair of pole pieces 80, 8d. The next pulse of current put through the coil 13, which is obtained through rectification of the positive half of the second cycle of the applied alternating current, causes the armature 12 to be pulled toward the other pair of pole pieces 80, 8:]. During the negative half of the second cycle, rectifier 15 does not conduct. there is thus no electromagnetic pull on the armature 12, and the latter is thus pulled back, by the restoring force built up in the spring arm 4 toward its neutral position. Thus, one cycle of movement of the armature 12, and hence also of the comb member 1, is completed for each two cycles of the alternating current supply, and the comb member 1 will thus vibrate or oscillate at a rate of thirty times per second, which is the desired rate.

In order for the mechanism to operate in the manner hereinabove described, wherein the armature 12 is caused to return and pass its neutral position in the negative half of each cycle of the alternating current so as to be within the field of pull towards the other pair of pole pieces, it is necessary for the mechanical resonant frequency of the vibratory organization, namely the spring arm 4, armature 12 and comb member 1, to be higher than thirty cycles per second or one-half the frequency of the rectified alternating current applied to the coil 13. Since the vibrating organization does not therefore reach resonance, it will be less sensitive to small changes in loading and spring constants.

It should be noted that, within its normal range of oscillatory movement, there is nothing for the armature 12, or the spring arm 4, to strike; the motion is completely free, since it is vertical motion and the pairs of pole pieces 8a, 8b and 8c, 8d are located in flanking relation to the spring arm 4 and its armature 12 rather than above the latter as in the hereinbefore mentioned patent No. 2,594,497. The stroke of the armature 12 is, how-- ever, stabilized, for should the armature tend to even shoot either pair of the pole pieces, it is immediately pulled back by the prevailing magnetic forces.

Various changes and modifications are considered to be Within the principle of the invention and the scope of the following claims.

What is claimed is:

1. In a doffer comb mechanism, a comb member, means for supporting and oscillating said comb member r in predetermined relation to the card clothing of a carding machine, including flexible arm means for mounting said comb member in spaced relation to a fixed support, and electromagnetic means for imparting vibratory oscillation to said arm means and therethrough to said comb member, said electromagnetic means including a core having two pairs of pole pieces arranged in spaced confronting relation, an armature carried by said arm means in the space between and flanked by said pairs of pole pieces for movement in alternation in the direction of each pair of pole pieces from a neutral position there Aw s between, a coil on said core, circuit means for connecting said coil to a source of alternating current having a frequency of the order of sixty cycles per second and a halfwave rectifier connected in said circuit, the movable assembly comprising said arm, armature and comb member having a mechanical resonant frequency higher than thirty cycles per second and an operational frequency of one-half that of said source of alternating current.

2. In a dofler comb mechanism, a comb member, and means for supporting and oscillating said comb member in predetermined relation to the card clothing of a card ing machine, including flexible arm means having one end thereof secured to a fixed support and the opposite end thereof carrying said comb member, and electromagnetic means for imparting vibratory oscillation to said arm means and therethrough to said comb member, said electromagnetic means including a core having two pairs of pole pieces arranged one above the other at the sides of said arm means adjacent to the end to which said comb member is secured, an armature carried by said arm means between and flanked by the pole pieces of each pair for movement toward each pair of pole pieces in alternation from a neutral position between the pairs of pole pieces, a coil on said core, circuit means for connecting said coil to a source of alternating current having a frequency of the order of sixty cycles per second and a half-wave rectifier connected in said circuit, the movable assembly comprising said arm, armature and comb member having a mechanical resonant frequency higher than thirty cycles per second and an operational frequency of 0ne-'ha1f that of said source of alternating current.

References Cited in the file of this patent UNlTED STATES PATENTS 1,493,259 Green May 6, 1924 1,645,794 Bumstead et al. Oct. 18, 1927 2,203,695 Murphy June 11, 1940 2,434,671 Murphy Ian. 20, 1948 2,594,497 Robinson Apr. 29, 1952 FOREIGN PATENTS 21,258 Great Britain of 1898 

